I got the below error while trying to accessing the upgraded mysqld server with a old client.
ERROR 1251: Client does not support authentication protocol
requested by server; consider upgrading MySQL client
I have resolved the above my updating the password as below.
update user set password=old_password(’new_password’) where user=’user_name’ and host=’10.0.0.2′;
and then try to access the mysqld server and now you will be able to connect to the server succesfully.